What is the name of the playable Assassin who defects from the Brotherhood in Assassin's Creed Rogue?

The playable Assassin who defects from the Brotherhood in Assassin's Creed Rogue is Shay Patrick Cormac.

Shay begins the game as an Assassin working with Achilles Davenport's Brotherhood in the eighteenth-century North Atlantic. After a disastrous mission involving an Isu site, he loses faith in the Brotherhood's methods and becomes convinced that its actions can cause catastrophic harm.

He then turns against his former allies and joins the Templars. Rogue presents the conflict from a Templar-aligned perspective, allowing players to hunt Assassins who would usually be treated as the series' protagonists.

Shay is not Liam O'Brien, his former Assassin companion, nor Adewale, a character associated with Assassin's Creed IV: Black Flag and Freedom Cry. Charles Dorian is Arno's father in Unity, another separate character.